The Metro-North New Haven Line will get an automatic braking system like the one being installed on the Spuyten Duyvil section of the Hudson Line in response to last week's deadly derailment, but it will take several months.

In the meantime, the railroad has imposed additional speed restrictions at two "critical" curves and five moveable bridges on the New Haven Line, Metro-North announced late Sunday evening.

"This accident has forced us to take another look," Metro-North spokeswoman Marjorie Anders said Monday. "Signal modification is the fix we've come up with."

The signal system changes would automatically slow down but not completely halt trains traveling above the maximum allowable speed of 30 miles per hour at the identified locations. The railroad is working toward installing a more advanced Positive Train Control system that would completely halt trains traveling in excess of maximum allowable speeds, but that's a longer-term project.

While the New Haven Line waits its turn to have the signal changes made, the railroad has imposed graduated speed limits around the curves and bridges.

The curves affected are located just west of the Greenwich station in Port Chester, and in Bridgeport. The bridges are those that cross the Mianus, Norwalk, Saugatuck, Pequonnock and Housatonic rivers.

Beginning Tuesday morning and until the revamped signal systems are up and running later this year on the New Haven Line, trains must slow to 30 mile per hour in the areas identified as needing the signal upgrades that will create a kind of automatic braking system.

The new speed restrictions are designed to ensure that train engineers gradually ratchet down speeds ahead of sharp curves or bridges, rather than barreling into them at high speeds and suddenly slowing down.

"This is ensuring trains go from 70 to 50, and 50 to 30, to make sure we don't have speed limit changes that exceed 20 miles per hour," Anders said. "It's formalizing what has been the practice."

Similar changes have been made on the other Metro-North lines. Altogether, the railroad has reduced maximum allowable speeds at 26 spots on the New Haven, Harlem, and Hudson lines.

The move follows an emergency order issued Friday by the Federal Railroad Administration to implement signal system changes that would automatically slow trains when engineers fail to brake when speed-restricted areas are approaching, and called for a series of additional interim safeguards until the signal systems are revamped.

Excessive speed has been highlighted as a cause of the derailment last Sunday on a sharply curved section of track near the Spuyten Duyvil station on the Hudson Line, which killed four people and injured more than 60 others. Federal investigators found from the train's on-board data recorders that the train was traveling at 82 miles per hour when it entered the curved section of track at Spuyten-Duyvil where the speed limit is 30 miles per hour.

The Federal Railroad Administration's order gave Metro-North a Dec. 31 deadline to submit an action plan to ensure the safety of passengers and employees on Metro-North.

Kevin Thompson, a spokesman for the Federal Railroad Administration, said the agency was aware of the changes Metro-North was making, but a formally submitted action plan detailing Metro-North's response by the end of the year is still required from the railroad.

"The Federal Railroad Administration is satisfied that Metro-North intends to comply with the directives of our Emergency Order," Thompson said Monday. "We will continue working directly with their staff as they implement its provisions."

Anders said the signal system plan and other changes to supervision and oversight should allow them to comply with most of the emergency order, but a more comprehensive document will need to be submitted for approval to comply with the Dec. 31 deadline.

She said addressing and designing signal changes for the curves in Port Chester and Bridgeport will require more work and time to correct than Spuyten-Duyvil because the spacing of interlockings near them is more complicated.

Interlockings are locations where trains can change from one track to another and also usually a place where two blocks of track are electrically separated for the purpose of sending signals about when trains are entering one section of track and leaving another.

"Each of the curves is unique," Anders said. "Designing signal systems changes for each one will be more difficult than what was achieved by a large team of signal experts working for about a week at Spuyten Duyvil and will require more significant infrastructure changes."

No cost estimate has yet been made, she said.

Additional oversight measures implemented to meet the FRA's requirements will include more Metro-North supervisors riding trains to track speeds, random audits of speed information from random train trips, and operating radar gun checks along the railways at critical spots, according to the railroad.

Last Tuesday after the derailment, Governor Dannel P. Malloy asked Metro-North to supply an action plan to address communication between the state and the railroad and explanations of the railroad's short and long term efforts to improve safety and public confidence in the New Haven Line.

"These actions, combined with investments in the infrastructure and a heightened focus on safety with all employees, are critical to ensure the confidence and trust of all the stakeholders of the Metro-North rail system," Connecticut Department of Transportation Commissioner Jim Redeker said in a statement. " It is our expectation that Metro-North will continue to make safety and reliability their primary focus and demonstrate this through regular and transparent actions and communications."